The Missouri River

The Missouri River is the longest river in North America, running about 2,341 miles (3,767 km) from the Rocky Mountains of Montana to its meeting with the Mississippi just above St. Louis. Nicknamed the "Big Muddy" for its heavy load of silt, it gathers the runoff of the northern Great Plains, draining a basin that covers roughly a sixth of the contiguous United States across some of the driest, emptiest country in the nation.

The river was the great route west — Lewis and Clark followed it toward the Pacific, and steamboats and wagon trains used its valley to push into the plains. In the 20th century a chain of massive dams and reservoirs was built across its upper course for flood control, power, and irrigation, taming the once-wild river and drowning long stretches of its valley. Below the dams it still carries the sediment that gave it its muddy name.